Surprisingly, never. "D'oh" is the creation of the voice behind Homer Simpson, Dan Castellaneta. In an early script, writers prompted Castellaneta to utter an "annoyed grunt" to convey Homer's frustration. On the fly, the voice actor interpreted "annoyed grunt" as "d'oh," a shortened version of 1930s actor James Finlayson's trademark "d'ooooh," which was often heard in Laurel and Hardy shorts of the era. As the catchphrase was entirely Castellaneta's idea and not the writers', Simpsons creator Matt Groening insisted that "d'oh" continued to be written as "annoyed grunt" in all Simpsons scripts. This edict carries even into song verses and episode titles that play upon "d'oh," such as the Old MacDonald riff, E-I-E-I-(Annoyed Grunt).
   (by: TechRepublic.com)